4-Hydroxy-3,3{40 ,4{40 -trichlorodiphenyl sulphone and alkali metal salts thereof

ABSTRACT

A halophenol of the formula   or alkali metal salt thereof. The compound is useful as a monomer in the preparation of aromatic sulphone polymers possessing improved fire resistance.

'United States Patent 1191 Leslie et al.

[ Nov. 4, 1975 4-HYDROXY-3,3',4-

TRICHLORODIPHENYL SULPHONE AND ALKALI METAL SALTS THEREOF [75] Inventors: Victor Jeffrey Leslie, Potters Bar; John Brewster Rose, Letchworth, both of England [73] Assignee: Imperial Chemical Industries Limited, London, England 22 Filed: Apr.26, 1974 21 Appl. No.: 464,700

Related US. Application Data [62] Division of Ser. No. 323,356, Jan. 15, 1973, Pat. No,

[30] Foreign Application Priority Data FOREIGN PATENTS OR APPLICATIONS 1,136,514 12/1968 United Kingdom 260/607 A OTHER PUBLlCATIONS J. Org. Chem. U.S.S.R-, PP. 2311-14 (1970).

Polymer (1972), Vol. 13, pp. 465-74 (Eng).

Primary ExaminerLewis Gotts Assistant Exa min'erD. R. Phillips Attorney, Agent, or FirmCushman, Darby & Cushman 57 ABSTRACT A halophenol of the formula Cl I 131 or alkali metal salt thereof. The compound is useful as a monomer in the preparation of aromatic sulphone polymers possessing improved fire resistance.

1 Claim, No Drawings 4-HYDROXY-3,3 ,4 TRICHLORODIPHENYL SULPHONE AND ALKALI METAL SALTS THEREOF This is a division of application Ser. No. 323,356, filed Jan. 15, 1973, now US. Pat. No. 3,830,781.

This invention relates to new aromatic polymers and to new chemical intermediates from which they may be produced.

In the specifications of British Pat. Nos. 1,153,035, 1,153,528 and 1,234,301 and Belgian Pat. No. 729,715 the disclosures of which are incorporated herein by reference, there are described methods for the production of aromatic polymers in which a dihalobenzenoid compound having each halogen atom activated by an electron-attracting group is caused to react with a substantially equivalent amount of an alkali metal hydroxide. The dihalobenzenoid compound may, in particular, have the formula where X and X are halogen atoms (preferably chlorine or fluorine) and A is a bivalent aromatic radical of, for example, benzene, naphthalene or biphenyl. Also described therein and in British Specification 'No. 1,177,183 (the disclosure of which is incorporated herein by reference) is the production of aromatic polymers whose molecular chains comprise units of the formula in which an alkali metal salt of a halophenol of the formula (where X is halogen) is polymerised by the displacement of alkali metal halide.

In British Specification Nos. 1,078,234 and 1,133,561 (the disclosure of which are also incorporated herein by reference), there is described a method for the production of aromatic polymers in which a dihalobenzenoid compound having each halogen atom activated by an electron-attracting group is caused to react with a di-(alkali metal) salt of a dihydric phenol in the liquid phase of an inert highly polar organic solvent. In particular, the dihalobenzenoid compound may have the formula (where X is halogen, preferably chlorine or fluorine) and the dihydric phenol may be one of the following:

(where the R group represents hydrogen, lower alkyl, lower aryl and the halogen-substituted groups thereof).

According to the present invention there are provided new aromatic polymers whose molecular chains comprise units of the formula CI Cl bd either alone or copolymerised with other units, and in particular with units of the formula Polymers containing units of the former formula are of higher fire resistance than equivalent polymers having units of the latter formula alone.

According to the invention there are also provided as a new chemical intermediates 4-hydroxy-3,3',4-tri-' chlorodiphenyl sulphone and the alkali metal salts thereof.

Of these compounds, 4-hydroxy-3,3,4'-trichlorodiphenyl-sulphone possessing a reactive chlorine atom as well 'as a phenolic group, can serve as a valuable chemical intermediate for producing a variety of products; for example the chlorine atom can be replaced by amino and substituted amino groups or by oxygenor sulphur-containing anions to produce amines, ethers and sulphides.

The alkali metal salts of this chlorophenol can be polymerised to give the new polymers of the invention.

This chlorophenol and its alkali metal salts may be prepared by for example the route outlined below in which the halophenol is made from the tetrachlorophenyl sulphone in a manner similar to that described for the halfway hydrolysis of bis-( 4-chlorophenyl) sulphone in British Specification No. 1,153,035.

,Cl Cl H0 6 SO, 6-(3 The alkali metal salt of the chlorophenol is initially I obtained dissolved in'the reaction medium and is preferably used directly,'-although for the purpose of purification it may be more convenient in some cases to acidify and then isolate gthe free chlorophenol. .This can be converted back into an alkali melal salt by treatment with a suitable base (e.g. an alkali metal hydroxide or alkoxide).

The alkali metal.v is conveniently potassium or sodium. Displacement of alkali metal halide often occurs more readily if the potassium cation is present in the reagent used, but the'weight (and usually the price) per mole of a potassium compound is higher than for the corresponding sodium compound. Some or all of the alkali metal cation in' the reagent may be replaced by an organic onium cation having a positively charged heteroatom (for example a quaternary ammonium cation such as tetramethyl ammonium) stable under the conditions of the reaction, and the term alkali metal salt as used herein is deemed to refer also to salts containing'such'onium cations.

Further according to the invention; there is provided a method for making new aromatic polymers having units of the formula CI CI in which an alkali metal salt of 4-hydroxy-3,3,4-trichlorodiphenyl sulphone or a mixture of 3,3,4,4'-tetrachlorodiphenyl sulphone and an equivalent amount of an alkali metal hydroxide or of the di-(alkali metal) salt of a dihydric phenol is polymerised at 150-400C by the displacement of alkali metal halide. These reagents may be polymerised alone, or they may be copolymerised with alkali metal salts of at least one other .activated halophenol (or with a mixture of at least one activated dihalobenzenoid compound and an equivalent amount of alkali metal hydroxide), in particular those described in British Specification Nos. 1,153,035 and 1,177,183; or they may be copolymerised with a mixture of di-( alkali metal) salt of at least one dihydric phenol and at least one activated dihalobenzenoid compound as described in British Specification Nos. 1,078,234 and 1,133,561. The halogen atoms in the halophenol or dihalobenzenoid compound are activated by electron-attracting groups such as SO ortho or para to the halogen atom. The comonomer may forexample be an alkali metal salt of a 4-(4-halophenylsulphonyl) phenol or a mixture of a bis(4- halophenyl) sulphone with an equivalent amount of alkali metal hydroxide. The halogen atoms in the comenomer are preferably chlorine (forcheapness) or fluorine (for greater reactivity), although the bromine derivativesmay also be used.

The polymerisation is preferably carried out in a polar liquid which is a solvent for alkali metal phenoxides and is stable under the reaction conditions employed, although an alkali metal salt of 4-hydroxy3,3 4"-trichlorophenyl sulphone may also be polymerised or copolymerised with another alkali metal salt of a halophenol in the melt.

Suitable polar liquids for the reaction include the lower dialkyl and cyclic alkylene sulphoxides and sulphones (e.g. dimethyl sulphoxide and 1,ldioxothiolan, aromatic nitriles (e.g. benzonitrile) and diary] ketones (e.g. benzophenone), sulphoxides and sulphones. The total amounttof solvent used is desirably sufficient to ensure that none of the starting materials are in the solid state in the reaction mixture.

Changing the liquid reaction medium may be convenient as-it allows the initial use of liquids that would be less suitable for the final stages, being for example inconveniently volatile or unstable at polymerisation temperatures or incapable of dissolving the resultant polymer to the desired extent. For example, dimethyl sulphoxide is a convenient solvent, especially for the hydrolysis; of 3,334,4f-tetrachloro-diphenyl sulphone withalkali metal hydroxide, but it cannot be used at such high temperaturesas 1,1-dioxothiolan (cyclic tetrarnethylene sulphone).

The liquid reaction medium need not contain any solvents for polymer of high molecular weight even at the later stages of the reaction, although if it does not the product is of relatively low molecular weight unless the final stage of polymerisation is carried out in the melt; this may be explained if the molecular chains of the polymer cease to grow in the solid state.

The rate of polymer formation in the reaction of the invention rises with rise of temperature and below 200C is usually uneconomically slow. It may, however, be advantageous to preheat the reaction mixture be tween C and 200C and then raise the temperature to produce the polymer. Temperatures up to 400C may be employed, and about 250C is usually convenient.

The,reaction should initially be carried out under pressure if necessary to prevent the escape of any dihalobenzenoid compound and any volatile solvent or cosolvent. Heating in vacuum may however be desirable at a later stage to remove unwanted solvents, e.g. dimethyl sulphoxide which may decompose at the temperatures required to produce high polymer.

The vessel used should be made of or lined with a material that is inert to alkali metal phenoxides and also to alkali metal halides under the conditions employed. For example, glass is unsuitable as it tends to react with phenoxide anions at high temperatures, upsetting the stoichiometry of the polymerisation and contaminating the product with silicate. Some grades of stainless steel undergo surface crazing at these temperatures in the presence of alkali metal halide, and vessels made of or lined with titanium or nickel or an alloy thereof or some similarly inert material-are preferable.

The polymerisation may conveniently be carried out in an extruder or on a heated'metal band.

To neutralise any reactive oxygenor sulphur-containiri'g anions, a reagent therefor may be introduced at the termination of the polymerisation. Reactive monofunctional halides, for example methyl chloride, are

particularly suitable.

The alkali metal halide can be removed from'the resultant high polymer by any suitablemeans. For example, it can be extracted from the high polymer using water, or the polymer itself can be dissolved in a strongly polar organic solvent (for example dimethyl formamide, 1-methyl-2-oxopyrrolidine, dimethyl sulphoxide, 1,1-dioxothiolan or nitrobenzene) and then rep'recipitated by addition to a liquid such as water which is miscible with the polymer solvent but itself is a nonsolvent for the polymer.

When the polymer is formed in solution, a conve-' nient procedure is to add the reaction mixture (which may be decanted or filtered from solid alkali metal hal-' ide) to an excess of a liquid which is miscible with the reaction solvent but in which the polymer is insoluble. 1f the reaction solvent is water-miscible, or is miscible with a liquid in which residual alkali metal halide also dissolves, the polymer can thus be obtained in one step. Otherwise, as for example if the reaction mixture is poured into methanol, the precipitated polymer initially contains alkali metal halide which can subsequently be washed out with water.

The reduced viscosity of the polymers of the invention is desirably at least 0.3 (measured at 25C at 1% w/v in a solvent such as dimethyl formamide) if they are to serve for structural purposes as a thermoplastic. In general, the new thermoplastic polymers of this invention may be used in any of the ways described for similar thermoplastic aromatic polysulphones in British Specification No. 1,016,245.

The following examples illustrate the invention.

EXAMPLE 1 Chlorosulphonic acid (1000 cm; 14 moles) was added dropwise to 1,2-dichlorobenzene (730 g; 5 moles) over a period of 3 hours. The temperature was maintained at less than 25 C and the reaction mixture was stirred. After addition, the mixture was allowed to stand for 3 hours and then poured into water (l0dm Chloroform (2 dm was added, insoluble solid filted off, and the chloroform layer separated, washed with water (2 X 1 dm) and dried over magnesium sulphate. Evaporation of the chloroform yielded a dark oil which on distillation gave a colourless oil (boiling point l15l20C/8 torr; 246 g) having infra red spectrum consistent with its being 3,4-dichlorobenzene sulphonyl chloride.

The insoluble solid was washed with water, dried under vacuum, recrystallised from acetic acid to yield colourless plates (melting point l79.5- 180C; 210 g) I which had infra red and nuclear magnetic resonance spectra (nmr) consistent with its being 3,3',4,4'-tetra- -chlorodiphenyl sulphone.

A sample of 3,3,4,4-tetrachlorodiphenyl sulphone (400 g; 1.12 moles) was suspended in dimethyl sulphoxide (2 dm) and the mixture was stirred under an atmosphere of nitrogen. To this mixture was added dropwise a solution of potassium hydroxide (2.24 mole) in water (300 cm and the resulting mix was heated at 100C for 2 hours. After initial darkening, the mix became pale yellow. The mix was then poured into aqueous hydrochloric acid (400 cm concentrated acid in 2 dm water) and a colourless oil, which solidified on cooling was formed. The solid was filtered off, washed with cold water, dried in vacuo at 100C, recrystallised from water to give colourless plates (melting point 196.5-197.5C; 368 g; 98% yield). The infra red and nmr spectra of the solid were consistent with its being 4-hydroxy-3,3,4'-trichlorodipheny1 sulphone. Thin layer chromotography using benzene/methanol (3:1 v/v) eluent on silica gel showed the presence of a single phenolic component in the reaction mix.

4-hydroxy-3,3 ,4-trichlorophenyl sulphone 192.7 g; 0.572 mole) was suspended in methanol (1.4 dm under nitrogen at 60C and aqueous potassium hydroxide (0.572 mole) was added. A yellow solution was formed which was concentrated under reduced pressure and evaporated to dryness to give a yellow powder. The yellow powder was dried under a high vacuum 0.01 torr) at 120C for 2 hours to yield the potassium salt of the trichlorophenol (216 g) which was stored over phosphorus pentoxide.

A sample (5 g) of the above potassium salt was placed in a tube which was evacuated 1 torr) for 30 minutes. The tube was then heated at 310C for 30 minutes, cooled to room temperature, opened and the contents dissolved in dimethyl formamide (20 cm). The solution was filtered and poured into methanol to precipitate a white solid which was washed with methanol and dried in vacuum 0.01 torr). The polymer had a reduced viscosity of 0.42 (as measured at 25C on a solution in dimethyl formamide containing 1 g of polymer in cm of solution) and had an nmr spectrum consistent with its having repeat units of the formula Cl Cl A film was compression-moulded at 300C and was found to have superior fire-resistance to a similar film made from a polymer prepared by the method described in Example 3 of British Specification No. 1,153,035 but having a reduced viscosity of 0.4.

EXAMPLE 2 A sample (30 g) of the potassium salt described in Example 1 and diphenyl sulphone (20 g) were heated at 230C for 17 hours under nitrogen. The solution was cooled to 160C, dimethyl sulphate (0.3 cm) added and the solution maintained at 160C for 1 hour. Dimethyl formamide (100 cm) was added, the solution filtered and then poured into a macerator containing methanol (500 cm). The colourless solid so formed was filtered off, diphenyl sulphone was extracted with hot methanol (3 X 500 cm) and with acetone/methanol (500 cm; 1:1 v/v), and the solid then dried at C. The solid was found to have a reduced viscosity of 0.3 (1% w/v in dimethyl formamide at 25C) and an nmr spectrum consistent with its having repeat units of the formula C I Cl a -e A film compression-moulded at 300C from the polymer had a fire-resistance similar to that of the film moulded from the polymer made by the procedure given in Example 1.

The polymer was found to be amorphous by X-ray crystallography and had a Tg of 210C as determined by Differential Scanning Calorimetry.

We claim:

1. A halophenol of the formula or alkali metal salt thereof. 

1. A HALOPHENOL OF THE FORMULA 